Pressure supply device

ABSTRACT

The invention relates to a pressure supply device for prioritised volume flow splitting, in particular in mobile working machines, comprising at least one adjusting pump (2) controllable by means of an LS signal as main pump, a constant-displacement pump (4) as an auxiliary pump, two pressure balances, a system to be supplied primarily, in particular in the form of steering hydraulics (PL), which outputs an LS signal, a system to be supplied secondarily, which outputs a further LS signal, in particular in the form of working hydraulics (PA), and a further system to be supplied hydraulically, in particular in the form of brake hydraulics (PB), wherein one pressure balance (DW1) is used to supply the system (PL) to be supplied primarily and/or the further hydraulic system (PB), the other pressure balance (DW2) is used to supply the system (PL) to be supplied primarily and/or the system (PA) to be supplied secondarily,

The invention relates to a pressure supply device for the prioritized distribution of a volume flow, in particular in mobile machines, consisting of at least one main pump designed as a variable displacement pump, which can be controlled by load-sensing signals, a fixed displacement pump as an auxiliary pump, two pressure maintenance-type components, a system to be supplied primarily, in particular in the form of steering hydraulics, which emits a load-sensing signal, a system to be supplied secondarily, in particular in the form of power hydraulics, that emits a further load-sensing signal, and a further system to be supplied hydraulically, in particular in the form of brake hydraulics.

Pressure supply systems of this type are known and are mainly used in mobile machines, in particular agricultural tractors. During the operation of such devices, for many phases of operation not all of the existing systems have to be simultaneously supplied with full volume flow, i.e. there is no danger of an under-supply of safety-relevant systems, such as steering. However, when special or extreme work situations occur, for example during certain maneuvers, such as those performed during fieldwork when turning at the headland, wherein steering systems, power hydraulics and possibly braking systems request the maximum volume flow, an under-supply may possibly occur. In view of this, it is state of the art, cf. DE 10 2004 005 606 B3, to throttle the return of a non-prioritized load in the case of an under-supply of a prioritized load, such as a power steering system, to ensure sufficient fluid pressure for the prioritized load. Similar known solutions provide for the use of an additional auxiliary pump, which can be operated to support the prioritized system, in particular in the form of a power steering pump.

In view of this, the invention addresses the problem of providing a pressure supply device of the type mentioned above, which is characterized by an uninterrupted service and a particularly favorable operational behavior.

According to the present invention, this problem is solved by a pressure supply device having the features of claim 1 in its entirety.

Accordingly, the invention provides a main pump and an auxiliary pump in the form of a variable displacement pump or a fixed displacement pump and a first and a second pressure maintenance-type component. In this case, the assigned fluid circuit is designed such that the first pressure maintenance-type component is used for supplying the system to be primarily supplied, such as the steering system, and/or the further hydraulic system, such as a trailer brake, that the second pressure maintenance-type component is used for supplying the system to be primarily supplied and/or the system to be secondarily supplied and that the respective pressure maintenance-type components can be controlled by a load-sensing signal, referred to below abbreviated as LS signal, in such a way that the fixed displacement pump is also used to supply the system to be secondarily supplied. The fact that the auxiliary pump even in normal operating conditions, in which there is no LS signal signaling the under-supply of the system to be primarily to be supplied (steering system), is used as an additional supply to support the variable displacement pump, results in a particularly safe and energetically favorable performance of device according to the invention.

Advantageously, the arrangement is such that the main pump directly supplies the system secondarily to be supplied with hydraulic fluid, the pressure of which can be preset, wherein the LS signal for the main pump is received from a shuttle valve, which compares the respective LS signals of the systems to be primarily and secondarily supplied and transmits the LS signal having the higher pressure to the main pump to control the latter.

In particularly advantageous exemplary embodiments, the output of the auxiliary pump is connected to the input of the first pressure maintenance-type component, the spring-loaded control side of which is additionally pressurized by the LS pressure on the output side of the shuttle valve or an LS-pressure, which, branched-off from the shuttle valve, relays the LS signal of the load to be supplied secondarily to this control side of the first pressure maintenance-type component.

Additionally, the spring-loaded control side of the second pressure maintenance-type component is pressurized by the LS-pressure, which, branched-off upstream of the shuttle valve, transmits the LS signal of the load to be primarily supplied to this control side.

The arrangement is advantageously made such that the two pressure maintenance-type components are pressurized by the control pressure of the load to be primarily supplied at their further control side arranged opposite from one of the control sides or that the other control side of the first pressure maintenance-type component is pressurized by the control pressure of the load to be secondarily supplied and the control pressure of the load to be primarily supplied is applied to the further control side of the other pressure maintenance-type component.

A check valve, which opens in the direction of the load to be primarily supplied, is installed in a connecting line between the outputs of the second pressure maintenance-type component, which is routed between the load to be primarily supplied and the load to be secondarily supplied, or a check valve is installed between one of the outputs of the second pressure maintenance-type component and the system to be secondarily supplied, which check valve closes in the direction of the output of the second pressure maintenance-type component, wherein the tap of the LS signal for the first pressure maintenance-type component is located in the supply line to the system to be secondarily supplied between this check valve and the feed point of the main pump.

A further check valve is installed between the two inputs of the two pressure maintenance-type components or between the input of the first pressure maintenance-type component and the output of the second pressure maintenance-type component, wherein the further check valve opens in the direction of the second pressure maintenance-type component.

A further check valve is arranged between the input of the second pressure maintenance-type component and the system to be primarily supplied, which check valve opens in the direction of this system, wherein the control line for the other control side of the second pressure maintenance-type component opens between this further check valve and this system.

Finally, a further check valve is installed between the supply line of the main pump and the input of the second pressure maintenance-type component, which opens in the direction of the second pressure maintenance-type component.

2/2-way pressure maintenance-type components or 3/2-way pressure maintenance-type components or a 2/2-way pressure maintenance-type component in combination with 3/2 pressure maintenance-type components can be used.

Below the invention is explained in detail with reference to exemplary embodiments shown in the drawing.

In the Figures:

FIG. 1 shows a symbolic representation of the hydraulic circuit of a first exemplary embodiment of the pressure supply device according to the invention; and

FIGS. 2 to 6 show representations corresponding to FIG. 1 of the hydraulic circuit of five further exemplary embodiments of the pressure supply device according to the invention.

In the figures, a main pump designed as a variable displacement pump is denoted by 2 and a fixed displacement pump used as an auxiliary pump is denoted by 4, both of which are fed from a storage tank 6. The output of the variable displacement pump 2 is directly connected to a load port PA via a pressure input P and a supply line 8, which load port is routed to a system to be secondarily supplied, such as power hydraulics. In all exemplary embodiments the output of the fixed displacement pump 4 is connected to an input a of a first pressure maintenance-type component DW1 via a pressure input P2. In the exemplary embodiment of FIG. 1 this is formed by a 3/2-way proportional directional valve, one control side d of which is pressurized by a spring 10 and to which an LS signal of a control line 12 is applied. The other control side c of the first pressure maintenance-type component DW1 is connected in the example of FIG. 1 via a control line 14 to the load port PL, which is routed to the system to be primarily supplied, in this case the steering, such that the control side c of the first pressure maintenance-type component DW1 is pressurized by the pressure of the load port PL. The output b of the pressure maintenance-type component DW1 is connected to a load port PB, which is routed to an OC load, such as a trailer brake. The further output e of the pressure maintenance-type component DW1 is connected to an input a of a second pressure maintenance-type component DW2, which, like the first pressure maintenance-type component DW1, is formed as a 3/2 proportional directional control valve in the example of FIG. 1. A control side d of the second pressure maintenance-type component DW2 is pressurized by the pressure of a spring 16 and an LS signal is applied via the control line 18. The other control side c of the second pressure maintenance-type component DW2 is pressurized by the pressure existing in the control line 14 and thus, like the first pressure maintenance-type component DW1, by the pressure of the load port PL.

In FIG. 1, the outputs e and b of the second pressure maintenance-type component DW2 are connected to a connecting line 20, one branch 22 of which is routed to the load port PL of the steering and the second branch 24 of which is routed to the load port PA of the power hydraulics. A check valve RV3 is installed in this connection line 20, which check valve in the example 20 of FIG. 1 opens in the direction of the load to be primarily supplied at the output port PL. The circuit of the example of FIG. 1 is completed by a shuttle valve WV, one input b of which receives the LS signal of the system to be primarily supplied, in this case the steering system, from the input port LSL and the other input a of which shuttle valve receives the LS signal of the system to be secondarily supplied, in this case the power hydraulics, from the input signal LSA. From the output c of the shuttle valve, the highest LS signal is transmitted as a control variable to the variable displacement pump 2 via the output port LS and to the control side b of the first pressure maintenance-type component DW1 via the control line 12.

Based on the circuit of FIG. 1, the following operation mode results:

The variable displacement pump 2 receives the highest load pressure reported in the system from the shuttle valve WV. The fixed displacement pump 4 is used as an additional supply to ensure a supply of the prioritized function (such as the steering system) and the OC function (in this case trailer brake) in case of failure of the variable displacement pump 2. Additional fixed displacement pumps may be provided as add-ons, each of which have a further pressure maintenance-type component (such as the pressure maintenance-type component DW1) to feed oil into the system if there is an additional volume flow demand of the overall system. The spring force of the pressure maintenance-type component springs 10 and 16 is lower than the control pressure difference of the variable displacement pump 2. If there is no under-supply of the loads at the load ports PL and PA, wherein the LS pressure of the respective loads is lower than the pressure effective at the load port by at least the control pressure difference, then the pressure maintenance-type component DW1 is switched against the force of the spring 10. Accordingly, there is no volume flow at the second pressure maintenance-type component DW2 to be divided. If necessary, any backflow of oil can be prevented by means of check valves at the load ports PL and PA. The load to be secondarily supplied at the load port PA is directly supplied via the supply line 8 of the variable displacement pump 2, and the load to be primarily supplied at the load port PL is supplied by the supply line 8 via the check valve RV3.

If there is an under-supply, wherein the working pressure at at least one of the loads is lower than the LS pressure feedback by the individual load plus the regulating pressure difference of the pump 2, then the balance of forces at the pressure maintenance-type component DW1 changes. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the second pressure maintenance-type component DW2, and accordingly, the volume flow to supply the further system to be supplied is minimized. In all the exemplary embodiments shown, this is the volume flow which is routed from the output d of the first pressure maintenance-type component DW1 via an OC supply line 26 to the load port PB, to which, for example, a trailer brake is connected as an OC load.

The pressure maintenance-type component DW2 regulates the volume flow additionally provided by the fixed displacement pump 4 via the pressure maintenance-type component DW1, which is provided for the prioritized load (steering system at PL). Before an under-supply occurs at the prioritized load, the pressure maintenance-type component DW2 moves in the direction of the spring force and increases the volume flow flowing to the prioritized load. The check valve RV3 prevents the oil from flowing from the prioritized load to the power hydraulics at the load port PA. If the volume flow of the fixed displacement pump 4 is at least as great as the maximum volume flow at the prioritized load, no under-supply can occur. If the volume flow at the prioritized load is smaller than the rated volume flow of the fixed displacement pump 4, then part of the volume flow can also be supplied to the power hydraulics via the pressure maintenance-type components DW1 and DW2.

The exemplary embodiment of FIG. 2 differs from the example of FIG. 1 in that the pressure maintenance-type components DW1 and DW2 are each formed by 2/2-way proportional valves and that two additional check valves RV1 and RV2 are provided. If there is no under-supply of the LS loads at the load ports PL and PA, the pressure maintenance-type components DW1 and DW2 are switched against the spring force. If the load pressure of the OC load connected to the load port PB is lower than the load pressure of the prioritized load to PL, the volume flow of the fixed displacement pump 4 can be supplied completely or partially to the OC load. Otherwise, the volume flow of the fixed-displacement pump 4 flows to the prioritized load at PL partially or completely via the check valves RV1 and RV2. If required, backward flow of oil from the power hydraulics (PA) to the pressure maintenance-type component DW2 can be prevented by a non-return valve at the outlet to the power hydraulics. The prioritized load (PL) is normally supplied by the variable displacement pump 2 directly via the check valve RV3.

If there is an under-supply at the LS loads, i.e. the working pressure at at least one of the loads PL, PA is lower than the LS pressure feedback by the individual load plus the regulating pressure difference of the pump 2, then the balance of forces changes at the pressure maintenance-type component DW1. The maximum LS pressure fed back via the shuttle valve WV plus the pressure equivalent force of the spring 10 are stronger than the pressure at the prioritized load PL, therefore, the pressure maintenance-type component DW1 is switched in the direction of the spring force. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the check valve RV1, and accordingly, the volume flow to supply the OC load connected at the output PB is minimized. The pressure maintenance-type component DW2 regulates the volume flow additionally provided by the fixed displacement pump 4 via the check valve RV1, which is provided for the prioritized load (PL). Before an under-supply occurs at the prioritized load, the pressure maintenance-type component DW1 moves in the direction of the spring force and increases the volume flow flowing to the prioritized load via the check valve RV2.

In the exemplary embodiment of FIG. 3, the first pressure maintenance-type component DW1 is formed by a 3/2 proportional directional control valve, and the second pressure maintenance-type component DW2 is a 2/2 proportional directional control valve. If there is no under-supply of the LS loads, the pressure maintenance-type component DW1 is switched against the spring force. The volume flow of the fixed displacement pump 4 is supplied to the OC load. If there is no under-supply, the pressure maintenance-type component DW2 is switched against the spring force, because the LS pressure of the prioritized load plus the pressure equivalent force of the spring 16 are smaller than the supply pressure at the prioritized load PL. If there is an under-supply at the LS loads, the pressure maintenance-type component DW1 is switched against the spring force. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the second pressure maintenance-type component DW2, and accordingly, the volume flow to supply the OC load to is minimized. Before an under-supply occurs at the prioritized load (PL), the pressure maintenance-type component DW2 moves in the direction of the spring force and reduces the volume flow flowing to the power hydraulics (PA). This increases the volume flow to the prioritized load via the check valve RV2.

In the example of FIG. 4, as in the example of FIG. 1, both pressure maintenance-type components DW1 and DW2 are formed by a 3/2 proportional directional control valve. In addition, a further check valve RV4 is provided. The pressure maintenance-type component DW2 regulates the volume flow intended for the prioritized consumer (steering). The inflow starts at the variable displacement pump 2 via the check valve RV4 or at the fixed displacement pump 4 via the pressure maintenance-type component DW1 and the check valve RV1. Before an under-supply occurs at the prioritized load, the pressure maintenance-type component DW2 moves in the direction of the spring force and increases the volume flow in the direction of the prioritized load. The pressure maintenance-type component DW2 ensures that the under-supply always occurs exclusively at the power hydraulics at the load port PA and not at the prioritized port PL. Due to the flow resistance of the pressure maintenance-type component DW2, the volume flow for the power hydraulics flows largely directly to the power hydraulics (PA) and not or only partially via the pressure maintenance-type component DW2. If there is no under-supply, the pressure maintenance-type component DW1 is switched against the spring force. The prioritized load (PL) is thus supplied by the variable displacement pump 2 directly via the check valve RV4 and the pressure maintenance-type component DW2. The volume flow of the fixed displacement pump 4 is then completely routed to the OC load via the pressure maintenance-type component DW1. If there is an insufficient supply to the load at the load port PA of the power hydraulics, the balance of forces changes at the pressure maintenance-type component DW1. Because the reported LS-pressure of the power hydraulics plus the pressure equivalent force of the spring 10 is stronger than the working pressure 5 at the load output PA of the power hydraulics, the pressure maintenance-type component DW1 is switched in the direction of the spring force. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred via the check valve RV1 in the direction of the second pressure maintenance-type component DW2, and accordingly, the volume flow to supply the OC load to is minimized. The check valve RV4 ensures that the volume flow can only flow to the pressure maintenance-type component DW2.

In the variant of FIG. 5, both pressure maintenance-type components DW1 and DW2 are formed by 2/2 proportional directional control valves. If there is no under-supply of the LS load at the output port PA of the power hydraulics, the pressure maintenance-type component DW1 is switched against the spring force. The prioritized load at PL is thus supplied by the variable displacement pump 2 directly via the check valves RV4 and RV2. If the load pressure of the OC load is lower than the load pressure of the prioritized load to (PL), the volume flow of the fixed displacement pump 4 can be supplied completely or partially to the OC load. Otherwise, the volume flow of the fixed-displacement pump 4 flows to the prioritized load at (PL) partially or completely via the check valves RV1 and RV2. If there is an insufficient supply to the LS load at the load port PA of the power hydraulics, the pressure maintenance-type component DW1 is switched in the direction of the spring force. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the pressure maintenance-type component DW2 and the check valve RV2 via the check valve RV1, and accordingly, the volume flow to supply the OC load to is minimized. The check valve RV4 prevents the direct inflow to the power hydraulics at PA. Compared to the variant of FIG. 4, there is an advantage in that the volume flow from the variable displacement pump 2 to the prioritized load (PL) is not routed via the pressure maintenance-type component DW2, i.e. pressure losses are minimized.

The circuit of FIG. 6 is similar to the variants of FIGS. 1 and 2, except that the pressure maintenance-type component DW1 is a 3/2 proportional directional control valve and the pressure maintenance-type component DW2 is a 2/2 proportional directional control valve. The pressure maintenance-type component DW2 in turn regulates the volume flow intended for the prioritized load (PL). The inflow starts at the variable displacement pump 2 via the check valve RV4 or at the fixed displacement pump 4 via the pressure maintenance-type component DW1. Before an under-supply occurs at the prioritized load (PL), the pressure maintenance-type component DW2 moves in the direction of the spring force and reduces the volume flow in the direction of the power hydraulics (PA). As a result, the volume flow in the direction of the prioritized load is increased via the check valve RV2. The pressure maintenance-type component DW2 ensures that the under-supply always occurs exclusively at the power hydraulics (PA) and not at the prioritized function (PL). Due to the lower flow resistance, the volume flow for the power hydraulics at PA flows directly to the power hydraulics and not or only partially via the pressure maintenance-type component DW2. If there is no under-supply of the LS load of the power hydraulics (PA), the pressure maintenance-type component DW1 is switched against the spring force and the prioritized load (PL) is thus supplied from the variable displacement pump 2 directly via the check valves RV4 and RV2. The volume flow of the fixed displacement pump 4 is supplied to the OC load in full. If there is an insufficient supply at the LS load of the power hydraulics (PA), the balance of forces changes at the pressure maintenance-type component DW1, resulting in it being switched in the direction of the spring force. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the second pressure maintenance-type component RV2, and accordingly, the volume flow to supply the OC load to is minimized. The check valve RV4 prevents the direct inflow into the power hydraulics. The advantage over the variants of FIGS. 1 to 3 is that the volume flow from the variable displacement pump 2 to the prioritized load (PL) does not run via the pressure maintenance-type component DW2. 

1. A pressure supply device for prioritized volume flow distribution, in particular in mobile machines, consisting at least of a variable displacement pump (2) as the main pump controlled by LS signals, a fixed displacement pump (4) as an auxiliary pump, two pressure maintenance-type components (DW1, DW2), a system to be primarily supplied, in particular in the form of a steering hydraulic (PL), which emits an LS signal, a system to be secondarily supplied that emits a further LS signal, in particular in the form of power hydraulics (PA), and a further hydraulically supplied system, in particular in the form of a hydraulic brake system (PB), wherein one pressure maintenance-type component (DW1) is used to supply the system (PL) to be primarily supplied and/or the further hydraulic system (PB), the other pressure maintenance-type component (DW2) is used to supply the system to be primarily supplied (PL) and/or the system to be secondarily supplied (PA) and wherein the respective pressure maintenance-type components (DW1, DW2) of an LS signal can be controlled such that the fixed displacement pump (4) is also used to supply the system to be secondarily supplied (PA).
 2. The pressure supply device according to claim 1, characterized in that the main pump (2) directly supplies the system (PA) secondarily to be supplied with hydraulic fluid, the pressure of which can be preset, and that the LS signal for the main pump (2) is received from a shuttle valve (WV), which compares the respective LS signals of the systems to be primarily (PL) and secondarily (PA) supplied and transmits the LS signal having the higher pressure to the main pump (2) to control the latter.
 3. The pressure supply device according to claim 1, characterized in that the output of the auxiliary pump (4) is connected to the input of one of the pressure maintenance-type components (DW1), the spring-loaded (10) control side (d) of which is additionally pressurized by the LS pressure on the output side (c) of the shuttle valve (WV) or an LS-pressure, which, branched-off from the shuttle valve (WV), relays the LS signal of the load (PA) to be supplied secondarily to this control side (d) of the first pressure maintenance-type component (DW1).
 4. The pressure supply device according to claim 1, characterized in that the spring-loaded (16) control side of the second pressure maintenance-type component (DW2) is additionally pressurized by the LS-pressure, which branched-off upstream of the shuttle valve (WV), transmits the LS signal of the load (PL) to be primarily supplied to this control side (d).
 5. The pressure supply device according to claim 1, characterized in that the two pressure maintenance-type components (DW1, DW2) are pressurized by the control pressure of the load (PL) to be primarily supplied at their further control side (c) arranged opposite from the one control side (d) or that the further control side (c) of the first pressure maintenance-type component (DW1) is pressurized by the control pressure of the load (PA) to be secondarily supplied and the control pressure of the load (PL) to be primarily supplied is applied to the further control side (c) of the other pressure maintenance-type component (DW2).
 6. The pressure supply device according to claim 1, characterized in that a check valve (RV3), which opens in the direction of the load (PL) to be primarily supplied, is installed in a connecting line (20) between the outputs (e and b) of the second pressure maintenance-type component (DW2), one branch (22) of which is routed to the load to be primarily supplied and one branch (24) of which is routed to the load to be secondarily supplied, or that a check valve (RV3) is installed between one of the outputs (b) of the second pressure maintenance-type component (DW2) and the system to be secondarily supplied (PA), which check valve closes in the direction of the output (b) of the second pressure maintenance-type component (DW2), and that the tap of the LS signal for the first pressure maintenance-type component (DW1) is located in the supply line (8) to the system to be secondarily supplied (PA) between this check valve (RV3) and the feed point (P) of the main pump (2).
 7. The pressure supply device according to claim 1, characterized in that a further check valve (RV1) is installed between the two inputs (a) of the two pressure maintenance-type components (DW1, DW2) or between the output (e) of a pressure maintenance-type component (DW1) and the input (a) the other pressure maintenance-type component (DW2) and that the additional check valve (RV1) opens in the direction of the other pressure maintenance-type component (DW2).
 8. The pressure supply device according to claim 1, characterized in that a further non-return valve (RV2) is arranged between the inlet (a) of the other pressure maintenance-type component (DW2) and the system (PL) to be primarily supplied, which opens in the direction of this system, and that the control line (14) for the other control side (c) of the further pressure maintenance-type component (DW2) opens between this further check valve (RV2) and this system.
 9. The pressure supply device according to claim 1, characterized in that a further check valve (RV4) is installed between the supply line (8) of the main pump and the input (a) of the further pressure maintenance-type component (DW2), which check valve opens in the direction of the further pressure maintenance-type component (DW2).
 10. The pressure supply device according to claim 1, characterized in that 2/2-way pressure maintenance-type components or 3/2-way pressure maintenance-type components and a combination of one 3/2-way pressure maintenance-type component and one or a 2/2-way pressure maintenance-type component are used as the pressure maintenance-type components (DW1, DW2). 